Abrasive article



Patented May 1, 1928.

A UNITED STATES PATENT OFFICE."

w ILr.IAM nunrou wnscorr, or noscron, MAssAgnusnr'rs, nssxenonsro RUBBER LATEX nnsnnnon conrona'rron, or nosrou, MASSACHUSETTS, A conronn'rron 4 OF MASSACHUSETTS.

No Drawing.

This invention relates to abrasive articles; and it comprises an abrasive article, such as an abraslve wheel, composed of abrasive grains bonded by a cured rubber binder reinforced b distributed asbestos fiber; all as more ful y hereinafter set forth-and as claimed.

Abrasive articleare ordinarily made of granules of an abrasive such as carborun dum (silicon carbid), emery, alundmn (fused alumina), etc., bonded together, hard rubber being frequently used as the binder. Rubber in this relation has many advantages and some disadvantages. In bonding with rubber 'on the mill, the abrasive grains are shattered and comminuted to some extent in thelong Work on the mill necessary to secure even distribution of the desirable application Serial No. 601,910, filed Nov.

18, 1922, zwhereon the present invention is in some respects an improvement, I have described a desirable way of making these articles. In this way latex is used as a source ofgbonding rubber. As it is a thin mobile liquid the assemblage of the abrasive grains .and binder becomes a simple mixing operation and no long mechanical work 1s necessary. llhereiore, no fiouring of the grains .occurs and it is possible to make extremelycompact wheels by using two grain sizes in the mix; these'grain sizes not being altered in mixing. By that invention I am able to reduce the. rubber binder tea very small amount; snaking a wheel which is practically all abrasive material without forfeiting any strength since the binder exists asvery thin layers or films. In the invention of the acknowledged application I have'further secured some-important advantages by incorporating a certain proportion of cotton or other vegetable fiber intothe rubber forming the bond of the wheel. ThlS fiber gives an extremely desirable reinforcement;

- a. reinforcement which is impossible 'to obtain on the mill. On the mill cotton is quick:

1y reduced to dust and particularly where abrasive grains form a component of the 'mix. In the present invent on I pifnoceed in much the same'way as in the ac owledged application, but in lieuof cotton. or other vegetable fiber I use asbestos. fiber.

Asbestos gives sufficient reinforcement for In another K ABRASIV'E ARTICLE.

Application filed January 11, 1927. Serial No. 160,532.

the present purposes and it is much more heat resistant, suffering less in 110mm: tion and in the use of the Wheel.

It is however a matter of some diiiiculty to incorporate ordinary commercial latex into asbestos fiber "since asbestos often exercises a specific coagula'tive power. Latex does not penetrate and permiate it prior to coagulation as it does with cotton fiber. The

asbestos can be freed'from this coagulative power however by a; preliminary extraction with acid. The acid extracted material is made fluilier and to that extent better adapt ed for the present'purposes and after washing and drying it becomes miscible with ordin'ary commercial latex; In another application Serial No. 161.026, filed January 13, 1927, I have described and claimed the manufacture of various asbestos-reinforced rubber articles by a process involving this principle. Latex may be made immune to the coagulative action of ordinary asbestos by the expedient of adding a protective colloid. Either of these expedients may be employed in making the abrasive articles of the present invention.

In a typical.embodiment of the present invention making a silicon carbid wheel bonded with rubber carrying an asbestos reinforcement, 1000 parts of granular abrasive, which may be in one or in two sizes, are mixed with 25 parts of good commercial asbestos and 100 parts of sulfur; mixing can be used and doing this has some advantages. Where a less degree of cure is wanted the quantity of sulfur is reduced to less than 50 parts. Thismixture is next formed into a dough with diluted latex, containing a protective colloid to prevent gcoagulation occurring during incorporation. As I use but a. small amount of rubber in'my bond, intimate and uniform distribution of the latex is required prior to any substantial sepnation of rubber therefrom. In this distribution the asbestos aids by asort of wick action and'it moreover holds the latex in place during drying; ,The best protective bolloid-I know for this purpose issthat proposed by one Day, being hemoglobin, or the e red end of blood as separated from the serum in a liquid separator. For the quantitles and materials so far specified I use 100 parts of rubber which can be. furnished by 300 parts by weight of commercial 30 per cent latex, dissolving in it 25 parts (dry basis hemoglobin. Instead of using protecte' latex and ordinary asbestos, I can use acid extracted asbestos and ordinary commercial latex; all quantities remaining the same. The dough is shaped into the desired article in any convenient Way; it may be extruded as rods; rolled into sheets, etc.

The molded article is next dried at a low temperature; which is best done in vacuo at a shelf temperature, toward the end of the drying, not exceeding 150 F. Under these conditions the water evaporates, leaving a porous article of the proper shape containing films of gelled rubber. This article is compacted under heavy pressure while still warm, giving the final shape and dimensions desired. Under pressure the clean hand latex now permeatesand cellular rubber surfaces weld together. The article is now cured or vulcanized, using the ordinary means and methods. Where the initial shape is a ,rod or tube, disks or wheels may be out from it at any stage in the described operation; and the same is true of sheets. Cutting after drying and before compaction is'generally best.

As stated, the same procedure may be followed Where the use of a protective colloid is not resorted to; the asbestos in this case being first extracted with acid. Commercial asbestos may be treated with boiling 5 per cent hydrochloric 'or sulfuric acid for 10 orv 15 minutes, washed free of acid and then dried. It no longer has any coagulative action on latex. On the other en'etrates it as it would an ordinary vegeta le fiber.

In the complete article -made under the present invention-the abrasive grains are, bonded and spaced by intervening films of hard rubber containing distributed asbestos as a reinforcing fiber. The rubber is an integral body enclosing and bonding the abrasive grains and containing and permeating the reinforcing fiber. The proportion or fiber being small it acts merely as a reinforcement and carrier for the rubber.

In this and other relations, I find there is a dividing line between rubber-fiber comer acting ment I am able to produce a wheel'lor,

other shape with a minimum amount of binder and, therefore, a maximum of abrasive, and yet one of great strength and resistance to shattering and chipping.

In abrasive wheels under the present i11- vention the major portion of the wheel is abrasive matter and the binder is present in but small amount. In this binder however the relation statedexists between the volume of'the rubber and that of the asbestos. In most embodiments of my invention I use gelled rubber; the form in which rubber isproduced by drying latex without coa ulation. Gelledrubber resembles long mil ed coagulationrubber and gives articles of great strength. Where coagulation rubtion, is as described.

What I claim is 1. An abrasive article composed of granules of abrasive material bonded together 'by films of gelled latex rubber, said rubber containing a minor amount of distributed asbestos fiber.

2. An abrasive article composed of granules of abrasive material bonded together by films of latex rubber, said rubber containing a minor amount of distributed asbestos fiber.

3. An abrasive article composed of granules of abrasive material bonded together by films of latexrubber, said rubber containing a minor amount of distributed asbestos fiber and also containing hemoglobin. In testimony whereof, I have hereunto afiixed my signature.

WILLIAM BURTON W ESTCOIT. 

